WSU Extension

Hortsense

Arborvitae : Berckmann's blight
(revision date: 4/11/2018)


Biology
Berckmann's blight is a fungal disease of the leaves and small twigs of Oriental arborvitae. Growth at the tips of branches is infected first, turning brown in late spring. As the infection moves down the branch, foliage becomes grayish. Branchlets and twigs may be girdled and die back, with foliage above the dieback turning reddish-brown. Tiny black fruiting bodies of the fungus may be present on infected foliage and where twigs are girdled. Infected foliage drops from the plant. The fungus overwinters on infected tissues and can be spread by splashing water, insects, or air movement. Repeated severe defoliation will eventually kill plants.
Management Options

Non-Chemical Management
  • Berckmann's arborvitae (Platycladus orientalis var. conspicua 'Berckmannsii') is especially susceptible. American and European arborvitae are not infected.
  • Prune out and destroy infected branchlets and twigs.
  • Avoid overhead watering.
  • Provide proper culture. Arborvitae plants require good drainage and air circulation to remain healthy.
Select non-chemical management options as your first choice!

Chemical Management

Apply twice in fall, with the first application in late September or early October and the second application in early November. Apply again in early spring (February to March) if disease is severe. Do not use Lilly Miller Microcop Fungicide in spring. Homeowners should not make foliar applications to trees over 10 ft tall. Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • Monterey Liqui-Cop Copper Fungicidal Garden Spray
    Active ingredient: copper-ammonia complex  |  EPA reg no: 54705-7
  • Phyton 27 Bactericide & Fungicide-Homeowner
    Active ingredient: copper sulfate, pentahydrate  |  EPA reg no: 49538-2
  • Soap-Shield Flowable Liquid Copper Fungicide [Organic]
    Active ingredient: copper octanoate  |  EPA reg no: 67702-2-56872
  • This list may not include all products registered for this use.
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Caption: Arborvitae Berckmann's blight
Photo by: R.S. Byther
Caption: Arborvitae Berckmann's blight
Photo by: R.S. Byther